xref: /webtrees/app/Factories/IdFactory.php (revision eeec557a973754cac923d5bfe748a55077cdabba) 
1<?php
2
3/**
4 * webtrees: online genealogy
5 * Copyright (C) 2022 webtrees development team
6 * This program is free software: you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation, either version 3 of the License, or
9 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program. If not, see <https://www.gnu.org/licenses/>.
16 */
17
18declare(strict_types=1);
19
20namespace Fisharebest\Webtrees\Factories;
21
22use Fisharebest\Webtrees\Contracts\IdFactoryInterface;
23
24use Ramsey\Uuid\Exception\RandomSourceException;
25use Ramsey\Uuid\Uuid;
26
27use function dechex;
28use function hexdec;
29use function str_pad;
30use function strtoupper;
31use function substr;
32
33use const STR_PAD_LEFT;
34
35/**
36 * Create a unique identifier.
37 */
38class IdFactory implements IdFactoryInterface
39{
40    /**
41     * @return string
42     */
43    public function uuid(): string
44    {
45        try {
46            return strtolower(strtr(Uuid::uuid4()->toString(), ['-' => '']));
47        } catch (RandomSourceException $ex) {
48            // uuid4() can fail if there is insufficient entropy in the system.
49            return '';
50        }
51    }
52
53    /**
54     * An identifier for use in CSS/HTML
55     *
56     * @return string
57     */
58    public function id(string $prefix = 'id-'): string
59    {
60        return $prefix . $this->uuid();
61    }
62
63    /**
64     * A value for _UID fields, as created by PAF
65     *
66     * @return string
67     */
68    public function pafUid(): string
69    {
70        $uid = strtoupper(strtr($this->uuid(), ['-' => '']));
71
72        if ($uid === '') {
73            return '';
74        }
75
76        return $uid . $this->pafUidChecksum($uid);
77    }
78
79    /**
80     * @param string $uid - exactly 32 hex characters
81     *
82     * @return string
83     */
84    public function pafUidChecksum(string $uid): string
85    {
86        $checksum_a = 0; // a sum of the bytes
87        $checksum_b = 0; // a sum of the incremental values of $checksum_a
88
89        for ($i = 0; $i < 32; $i += 2) {
90            $checksum_a += hexdec(substr($uid, $i, 2));
91            $checksum_b += $checksum_a & 0xff;
92        }
93
94        $digit1 = str_pad(dechex($checksum_a), 2, '0', STR_PAD_LEFT);
95        $digit2 = str_pad(dechex($checksum_b), 2, '0', STR_PAD_LEFT);
96
97        return strtoupper($digit1 . $digit2);
98    }
99}
100